PILLOWS AND SCRATCHES EarthCache
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Located on top of a road cut east of Ely, MN on Highway 169. .I WILL DELETE ANY SPOILERS (LOGS/PICTURES) THAT INDICATE WHERE THE CACHE IS LOCATED.
Step one: Go to N47 54.426 W091 50.812- refer to my cache GCNJ6J to get a full explanation of ellipsoidal “pillow” lava formations. What you need to observe is the eroded “pillows” – unusual because they are three dimensional. Once you have read about the formation and observed the “pillows” go on to step two.
Step two: N47 54.688 W091 48.983
PART1: On top of the road cut, observe the area (you will have to walk around on the bare rock) and look for scratches and grooves. These are GLACIAL STRIATIONS (A linear scratch on a rock left by a rock embedded in moving glacial ice.) The last glacial period moved through here +/- 10,000 years ago.
QUESTION TO ANSWER: With the knowledge that glaciers came from colder climates, using your GPS compass or another compass, observe the striations and grooves and TELL ME WHAT COMPASS DIRECTION THE GLACIER WAS MOVING.
PART 2: In STEP ONE, you observed three dimensional “pillows” that eroded from a matrix of greenstone. At this location you can see the internal structure of several of these “pillows”. The tops of these “pillows” were eroded off by the glacier that also made the striations. Observe that a “pillow” consists of a darker outer “skin” about1- 2 inches wide, and an inner core of lighter material. (This lighter material is eroded - if you look at a chipped piece you will see that the matrix is really dark).These “pillows” were formed underwater when hot volcanic lava erupted into the cold water of a sea that once covered the area. The molten lava which hits the cold water first is the finest grain rock when cooled.
QUESTION TO ANSWER: Observe the “skin” and core and TELL ME which hit the cold water first- the “skin” or the core of the “pillow"?
Additional Hints
(No hints available.)